1. Field of the Invention
The present invention relates to compositions and methods for treating, suppressing, controlling, and/or preventing citrus canker and other plant diseases inhibited by copper.
2. Description of Relevant Art
The United States Department of Agriculture has reported that citrus canker is a disease caused by the bacterium Xanthomonas axonopodis pv. Citri, which can cause extensive damage to twigs, leaves, and fruit of susceptible citrus varieties. The disease often causes fruit to drop prematurely and to be unmarketable because of lesions on the peel. The bacteria that cause citrus canker can survive for extensive periods on citrus branches and bark. The disease is spread by wind, rain splash, mechanical activities (such as pruning, picking, and spraying carried out within and between groves), movement of infected plants or plant parts, and the activity of birds, insects, and/or mammals. Citrus canker threatens the citrus growing areas of the United States because of its rapid spread, high potential for damage, and impact on exports to foreign countries and interstate movement.
The University of Florida has reported that over the last 30 years, the Institute of Food and Agricultural Sciences has evaluated dozens of products for canker control, including antibiotics, compounds that reduce resistance in plants, and disinfectants, and none have proven more effective than copper products. Copper products are considered to be quite effective in preventing infection of fruit, less effective for reducing leaf infection, and of limited value in reducing spread of the disease. While applying copper to young leaves generally protects them against infection, such protection is soon lost due to rapid expansion of the surface area as the leaves grow. Fruit grows more slowly and is easier to protect. However, fruit is susceptible to infection after the stomates open, when the fruit is about ½- to 1-inch in diameter, until they develop resistance, and infection through wounds can occur at any stage.
Despite the utility of copper products in treating citrus canker, the University of Florida has advised that copper use should be minimized because copper accumulates in soil and may cause phytotoxicity and environmental concerns. Citrus canker is predicted to be difficult to control. According to the University of Florida, approximately 75% of the citrus acreage in Florida is already within 5 miles of a canker find. An ongoing need exists for improved compositions and methods for treating and controlling citrus canker.